[Development] Qt branches & proposal how to continue with those

[Jani Heikkinen]

Hi,

We have currently really many branches open:
- 5.6
- 5.9
- 5.10
- 5.10.1
- 5.11
- dev

In my opinion this is too much to handle effectively, especially because there is many branches in stable mode (see http://code.qt.io/cgit/meta/quips.git/tree/quip-0005.rst). Currently '5.6' is in 'strict' mode and  '5.9', 5.10' & '5.11' are in stable... I think we need to change that to be able to work efficiently & get releases out. 

So I am proposing following changes starting from 1st Feb 2018:

- '5.6' will move in 'very strict' mode 
- '5.9' will move in 'strict' mode. So no direct submissions anymore, just cherry picks from stable
- '5.10' will be closed and Qt 5.10.1 will be the final release from Qt 5.10 series (5.6 and 5.9 are LTS branches so we shouldn't keep Qt 5.10 active too long)
- '5.11' will be to one and only stable branch

br,

Jani